1. Field of the Invention:
This invention relates to elastomeric compositions which are useful at elevated temperatures and pressures found in oil and gas wells and to devices made from such compositions.
2. Description of the Prior Art:
High gas pressures often exist in oil and gas wells which cause rubber parts of downhole tools to blow-up or "bubble". The gas induced bubbling is apparently caused by gas permeating the rubber at high pressure, and, upon removal of the tool from the hole, the sudden reduction in pressure occurs before the gas can escape, resulting in bubbling of the rubber elastomer.
A particular problem area is in the stator component of downhole pumps used to lift oil and gas constituents from the well. The stator is a double internal helix precision molded of a synthetic elastomer which is permanently bonded in a steel housing. The stator is suspended from a tubing string and cooperates with a mating rotor which defines a sealed cavity within the pump. The rotor is driven from the surface, as by a sucker rod. As the rotor turns within the stator, the cavities progress in an upward direction. The elastomer used for the stator must be highly resistant to the most severe downhole conditions and resist delamination and bubbling.
U.S. Pat. No. 3,926,900, issued Dec. 16, 1975, to Guzy et al., teaches blends of EPDM with liquid, 1,2-polybutadiene which are peroxide cured and are surprisingly resistant to degradation at elevated temperatures and pressures within oil and gas wells. These blends are extremely useful in electrical insulating materials, particularly in wire and cable constructions.
U.S. Pat. No. 4,430,472, issued Feb. 7, 1984, to Guzy, teaches jacketing compositions for electrical wires and cables which are comprised of ethylene/acrylic elastomers which have blended therewith a liquid polybutadiene.
While the above compositions work well for their intended application, they have not successfully solved the problem of bubbling and delamination in progressive cavity pumps.
The present invention has as its object to eliminate bubbling and delamination in parts of downhole tools.
Another object of the invention is to improve the life span of downhole tools having elastomeric components when the components are used in wells having high gas to oil ratios.